Electrical add/drop multiplexers are widely used in fiber optic networks to terminate fibers at customer premises such as houses and offices. An electrical add/drop multiplexer converts optical signals received from the fiber optic network to electrical signals for use by equipment at a customer premise such as cable modems, set-top boxes, IP phone, IP video adapters, wireless routers, or any other equipment. An electrical add/drop multiplexer also converts electrical signals received by equipment at a customer premise to optical signals for transport by a connected fiber to a remote destination.
An electrical add/drop multiplexer includes wavelength selective elements that are used to provide specific wavelength ranges of the light present on a fiber to respective electro-optical components of the multiplexer. The electro-optical components of the electrical add/drop multiplexer convert the light received to electrical signals. For example, the wavelength selective elements of the electrical add/drop multiplexer may be used in conjunction with respective electro-optical components to provide at separate outputs of the multiplexer voice, data, video, and/or telemetry signals that are combined on the input fiber. The electrical add/drop multiplexer also may include an electro-optical component for converting digital data to light at a specific wavelength range for transport by the fiber to a remote location.
However, electrical add/drop multiplexers lack flexibility. That is, electrical add/drop multiplexers are useful only for those specific wavelength ranges of light that the electro-optical components of the multiplexer can process. Accordingly, if there is a need to process light at different wavelengths, then the electrical add/drop multiplexer must be upgraded with additional components.
For example, FIG. 2 illustrates an electrical add/drop multiplexer 200 used to process light at specific wavelengths. Electrical add/drop multiplexer 200 includes a fiber connector 202 connected to a collimator subassembly 203; an optical wavelength selective filter 205; a receiver 207; and a transmitter 210.
A fiber 201 from the optical network terminates at the fiber connector 202, and the collimator subassembly 203 generates a collimated beam 204. Filter 205 passes a specific wavelength of the collimated beam 204 to receiver 207. Receiver 207 converts the optical signal received to electrical signals for use by external equipment. Transmitter 210 converts electrical signals received from external equipment to optical signals of a specific wavelength, which then passes through filter 205, collimator sub-assembly 203, and fiber connector 202 for transport by fiber 200 to a remote destination.
FIG. 3 illustrates the additional components needed to upgrade the electrical add/drop multiplexer 200 of FIG. 2 to process additional light at different wavelengths (i.e., “upgraded wavelength(s)”). More specifically, an optical add/drop multiplexer 300′ and a second add/drop multiplexer 300 are added to electrical add/drop multiplexer 200 to process additional light at the upgraded wavelengths.
In the upgraded system, the fiber 301 from the optical network terminates at the optical add/drop multiplexer 300′ instead of the electrical add/drop multiplexer 200. The optical add/drop multiplexer 300′ couples light in a particular wavelength range that includes the upgraded wavelengths to an upgrade fiber 311 that is connected to the second add/drop multiplexer 300. The optical add/drop multiplexer 300′ couples the other wavelengths of light from fiber 301 to fiber 201. The second add/drop multiplexer 300 may be designed to process light at the upgraded wavelengths that are received on fiber 311.
The electrical add/drop multiplexer 300 is similar to electrical add/drop multiplexer 200 except that filter 306 passes to receiver 308 a different wavelength (i.e., one of the upgraded wavelengths) of light received from the optical network than the wavelength of light passed by filter 205. Similarly, transmitter 309 converts electrical signals received from external equipment to optical signals of a different wavelength (i.e., one of the upgraded wavelengths) than the wavelength of the optical signal from transmitter 210. The optical signals of the upgraded wavelength pass through filter 306, collimator sub-assembly 303, fiber connector 302, and upgrade fiber 311. The optical add/drop multiplexer 300′ combines the light from upgrade fiber 311 transmitted from transmitter 309 with the light from the fiber 201 transmitted from transmitter 210 for transport by fiber 301 to a remote destination.
As illustrated by FIG. 3, upgrading an existing electrical add/drop multiplexer to process light at different wavelengths requires multiple additional components, which is costly and inefficient. Accordingly, as the number of new services provided at different wavelengths of light continues to grow, so does the need to reduce the cost to upgrade existing equipment at the customer premise to provide these additional services will grow.